The major focus of this research proposal is on the early processing of auditory information. The principal tool used in this endeavor is an event-related potential termed the mismatch negativity (MMN). Research with the MMN has uncovered a system located in auditory cortex that detects change in the acoustic environment on an automatic, pre-attentive basis. The proposal has four basic aims. One aim pertains to a pattern of MMN results obtained in the previous grant period suggesting that object formation occurs pre-attentively in the auditory system. One study will study examine the features that induce grouping of acoustic input. Another study will attempt to extend the finding to different acoustic features and will ascertain whether, in addition MMNs are elicited by switching from one object to another. A second aim is to ascertain whether MMNs are associated with illusory percepts. One study will examine illusory speech perceptions (the McGurk effect) and one study will examine illusory non-speech perceptions (the ventriloquist effect). The third aim is to establish neuronal generator sources for the MMN using fMRI. One fMRI study will attempt to localize the generator sources for MMNs associated with acoustic features (frequency and stimulus duration) and an abstract rule concerning acoustic features. Another fMRI study will attempt to localize the generator sources for MMNs associated with speech stimuli